1. Field of the Invention
This invention relates to a method and apparatus for forming a rolled rim at the mouth of a cup or container which has a body that is fabricated from a sheet of a thermoplastic material.
2. Description of the Prior Art
U.S. Pat. No. 3,854,583 (Amberg et al.) discloses a container that includes a body which is fabricated from a sheet of an expanded thermoplastic material and which is provided with a rolled rim or bead at the mouth of such container. Such rolled rim or bead helps to stiffen the container at the mouth thereof, it provides a smooth edge for drinking a beverage from the container, and it provides a protrusion from the sidewall of the container that is useful in securing a cap or closure to the container. Containers of the type illustrated in the aforesaid U.S. Pat. No. 3,854,583 have been extensively utilized as cups for single service quantities of a beverage, for example, coffee, and, when so utilized, the bodies of such containers have typically been manufactured in a nestable or frustoconical configuration from rectangular blanks of a heat-shrinkable thermoplastic material by a process which includes the shrinking of a cylindrical sleeve formed from such blank against the outer surface of a frustoconical forming mandrel. Typically, such cups have been produced by apparatus similar to that disclosed in U.S. Pat. No. 4,053,346 (Amberg et al.), and may also be produced by apparatus similar to that disclosed in U.S. Pat. No. 4,072,549 (Amberg et al.).
In the manufacture of cups of the type described in the aforesaid U.S. Pat. No. 3,854,583, either by apparatus of the type-described in the aforesaid U.S. Pat. No. 4,053,346 or by the apparatus of the type described in the aforesaid U.S. Pat. No. 4,072,549, heretofore it has been necessary to effect rotation of the cup relative to the rim-forming tooling of the apparatus during the rolling of the rim in the body of the cup to obtain a properly formed and rolled rim. As is clear from each of the aforesaid U.S. Pat. Nos. 4,053,346 and 4,072,549, it is necessary to provide rather complex apparatus to effect such relative rotation between each of the cups and the rim-forming tooling that is used to roll rims in such cups, and the complexity of such apparatus adds to the initial expense in manufacturing such apparatus and to subsequent expenses related to its maintenance and operation.